Owner's Manual
Page 11
... display during power interruptions. The warning flashes about two months before leaving home for backup power) if your thermostat was wired to run on AC power when installed. Batteries provide backup power to remove thermostat from wallplate. All settings are depleted. M29422 PRO TH3110D / TH3210D M29421 Batteries are optional (for more than a month...
... display during power interruptions. The warning flashes about two months before leaving home for backup power) if your thermostat was wired to run on AC power when installed. Batteries provide backup power to remove thermostat from wallplate. All settings are depleted. M29422 PRO TH3110D / TH3210D M29421 Batteries are optional (for more than a month...